A method for producing a structured lipid containing medium-chain or short-chain fatty acids

Abstract

The present invention discloses a production method of a structured lipid containing medium-chain or short-chain fatty acids, comprising: S1, mixing a raw material oil and a liquid lipase in an enzyme-oil micro-mixer M1 to form an emulsified oil containing the liquid lipase; S2, starting a feed pump P3, and after preheating medium-chain triglycerides or short-chain triglycerides through a second preheating pipe L2, feeding them into a reaction micro-mixer M2 to carry out hydrolysis and transesterification reactions with the emulsified oil, using a delay pipe L3 to extend the reaction time to make the reaction reach equilibrium, and then subjecting the reaction product after the reaction to high-temperature enzyme inactivation through a quenching pipe L4, and then releasing and flowing out through a back pressure valve BPV. The present invention uses a liquid lipase as a catalyst and adopts a microchannel reaction system for production, which improves the mass transfer efficiency between the lipase and the oil and has the advantages of high reaction efficiency, fast reaction speed and low production cost. It not only improves the mass transfer efficiency between the lipase and the oil, but also realizes the continuous production of the structured lipid containing medium-chain or short-chain fatty acids, and improves the production efficiency of the structured lipid containing medium-chain or short-chain fatty acids.

Description

Technical Field

[0001] The present invention relates to the field of preparation of structured lipids, and in particular to a production method of a structured lipid containing medium-chain or short-chain fatty acids. Background Art

[0002] Most natural animal and vegetable oils and fats are long-chain fatty acid triglycerides. Long-chain fatty acid triglycerides are metabolized slowly in the human body, and the excess fat is mostly stored in subcutaneous fat or human organs, which is one of the main reasons for human obesity. At present, the per capita oil intake in China has reached more than twice the recommended standard of the Chinese Nutrition Society, and the metabolic syndrome caused by obesity greatly affects the health level of the Chinese people.

[0003] In recent years, structured lipids containing medium-chain fatty acids and short-chain fatty acids have received increasing attention. For example, medium-chain triglycerides (MLCT) have special physiological functions such as rapid energy supply, reducing serum cholesterol content, preventing and alleviating obesity, and are the most promising substitutes for edible oils at present; another example is that long-chain and short-chain triglycerides containing butyric acid can not only reduce the intake of long-chain fatty acids, but the butyric acid in the oil has multiple protective effects on colon wall cells, and also has functions such as nourishing brain nerves, reducing fat accumulation, controlling fatty liver, reducing blood sugar, and increasing skeletal muscle mass.

[0004] At present, medium-chain triglycerides and long-chain and short-chain triglycerides (medium-chain triglycerides and long-chain and short-chain triglycerides are collectively referred to as structured lipids) can be prepared by enzymatic transesterification or chemical transesterification reaction technology. The chemical transesterification method not only has defects such as poor reaction specificity, cumbersome reaction steps, and the need for a large amount of chemical reagents, but also inevitably has the situation of chemical reagent residues, which does not meet the requirements of food safety. Therefore, in the food and health care industry, enzymatic transesterification technology is mostly used to prepare structured lipids.

[0005] Lipase is a kind of biocatalyst, which is non-toxic and edible, and is the most commonly used catalyst for the preparation of structured lipids by enzymatic transesterification. Using a constant temperature shaker as the reactor, soybean oil and glyceryl triacetate as raw materials, and Lipozyme RM IM lipase as the catalyst, medium- and long-chain triglycerides containing acetic acid were synthesized in a solvent-free system with an enzyme addition amount of 10% and a substrate molar ratio of 2.5:1 (Caoli Cao. Study on the Enzymatic Preparation and Characteristics of Low-Calorie Structured Lipids [D]. Hefei: Hefei University of Technology, 2015); using glyceryl tributyrate and methyl stearate as raw materials, and Lipozyme RM IM lipase as the catalyst, medium- and long-chain triglycerides containing butyric acid were synthesized in a solvent-free system. Under the conditions of an enzyme addition amount of 10.34%, a molar ratio of methyl stearate to glyceryl tributyrate of 1.77:1, and a reaction temperature of 65 °C, a structured lipid containing butyric acid was synthesized (Lu Han. Solvent-Free Enzymatic Catalytic System for the Synthesis of Low-Calorie Short- and Long-Chain Triglycerides [D]. Wuxi: Jiangnan University, 2012). However, in the above transesterification for the preparation of structured lipids, immobilized lipase is used as the catalyst, and most of the lipases are immobilized lipases. The enzymatic transesterification reaction can be carried out in a stirred-tank reactor by high-speed stirring in industry, or the lipase can be immobilized in a fixed bed. The high cost of using immobilized lipase restricts the industrial development of medium- and long-chain triglycerides and medium- and long-chain triglycerides to a certain extent.

[0006] Liquid lipase is refined by deep fermentation, which can hydrolyze the ester bond of oil molecules to produce fatty acids, monoglycerides and diglycerides, and has been widely used in industries such as animal gelatin, fur, leather, textile washing, etc., with low cost. Using liquid lipase as the catalyst can greatly reduce the production cost. Research shows that lipase needs a certain amount of water to be activated. Liquid lipase can provide the enzyme and water required in the reaction, and can adjust the water content in the reaction system by adjusting the enzyme concentration. However, liquid lipase is immiscible with oil, and the reaction only occurs at the two-phase interface, with low mass transfer efficiency and long reaction time. Therefore, how to improve the mass transfer efficiency and reaction rate is an urgent problem to be solved in the existing technology. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a method for producing a structured lipid containing medium-chain or short-chain fatty acids. This method uses a microchannel reaction system, which not only improves the mass transfer efficiency between lipase and oil, but also realizes the continuous production of structured lipids containing medium-chain or short-chain fatty acids, thereby improving the production efficiency.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] The production method of a structured lipid containing medium-chain or short-chain fatty acids according to the present invention uses a microchannel reaction system to prepare a structured oil ester containing medium-chain or short-chain fatty acids, and includes the following steps:

[0010] S1, Set the pressures and flow rates of the feedstock oil feed pump P1 and the liquid lipase feed pump P2, and then start the feedstock oil feed pump P1 and the lipase feed pump P2 to mix the feedstock oil and the liquid lipase in the enzyme-oil micro-mixer M1 to form an emulsified oil containing the liquid lipase.

[0011] S2, Start the hot water circulation pump and set the system temperature. After the working conditions are stable, set the pressure and flow rate of the triglyceride or short-chain triglyceride feed pump P3 and start the medium-chain triglyceride or short-chain triglyceride feed pump P3. The medium-chain fatty acid triglyceride or short-chain fatty acid triglyceride is preheated by the second preheating tube L2 and then enters the reaction micro-mixer M2 to carry out hydrolysis and transesterification reactions with the emulsified oil. The delay tube L3 is used to extend the reaction time to make the reaction reach equilibrium. The reaction product after the reaction is subjected to high-temperature enzyme inactivation through the quenching tube L4 and then flows out after being released by the back pressure valve BPV to obtain a structured lipid containing medium-chain or short-chain fatty acids.

[0012] In the above solution, the present invention uses edible oil, medium-chain fatty acid triglyceride or short-chain fatty acid triglyceride as raw materials and liquid lipase as a catalyst, and adopts a microchannel reaction system for production, which improves the mass transfer efficiency between the lipase and the oil and has the advantages of high reaction efficiency, fast reaction speed and low production cost. It not only improves the mass transfer efficiency between the lipase and the oil, but also realizes the continuous production of the structured lipid containing medium-chain or short-chain fatty acids and improves the production efficiency of the structured lipid containing medium-chain or short-chain fatty acids.

[0013] In the present invention, after the S2, the refining of the reaction product is further included, specifically including: distilling the reaction product after high-temperature enzyme inactivation by using a molecular distillation system, and the distillation conditions of the molecular distillation system are: the molecular distillation vacuum degree is 1-10 Pa; the evaporation temperature of the molecular distillation is 160-180 °C. The present invention uses molecular distillation to remove the free fatty acids and unreacted medium-chain fatty acid triglycerides or short-chain fatty acid triglycerides in the product.

[0014] Preferably, the enzyme-oil micro-mixer M1 and the reaction micro-mixer M2 are separation-recombination type or star-layer type microchannel mixers, the channel diameter ≤ 1000 μm, the liquid holdup is 50-1000 μL, and the flux is 4-3000 L / h.

[0015] In the present invention, the first preheating tube L1, the second preheating tube L2, the delay tube L3 and the quenching tube L4 are all coil heat exchangers or stainless steel coils placed in a constant temperature water bath.

[0016] During laboratory-scale production, the first preheating tube L1, the second preheating tube L2, the delay tube L3, and the quenching tube L4 are preferably stainless steel coiled tubes placed in a constant temperature water bath. They are all made of φ3mm×6m stainless steel tubes. According to the reaction temperature requirements of the reaction system, the first preheating tube L1, the second preheating tube L2, and the delay tube L3 are placed in a constant temperature water bath at 30 - 70°C, and more preferably, the temperature of the constant temperature water bath is set at 40 - 50°C; the temperature of the constant temperature water bath of the quenching tube L4 is set at 90 - 100°C to inactivate the lipase in the reaction product at high temperature.

[0017] During industrial production, the first preheating tube L1, the second preheating tube L2, the delay tube L3, and the quenching tube L4 are preferably shell-and-tube heat exchangers, and the reaction temperature and inactivation temperature are controlled by controlling the temperature of the working medium.

[0018] In the present invention, the raw material oil is edible oil, preferably vegetable oils such as soybean oil and corn oil; the liquid lipase is a commercial lipase obtained by deep fermentation of Aspergillus niger or Aspergillus oryzae; the medium-chain fatty acid triglycerides include any one or a combination of two or more of glyceryl trioctanoate, glyceryl tridecanoate, or caprylic / capric acid triglyceride; the short-chain fatty acid triglycerides include any one or a combination of two or more of glyceryl triacetate, glyceryl tripropionate, or glyceryl tributyrate.

[0019] In the present invention, the feeding flow rate ratio of the raw material oil, medium-chain or short-chain fatty acid, and liquid lipase is 100:10 - 100:3 - 10; the addition amount of lipase is 300 - 3000U / g of oil.

[0020] Compared with the prior art, the present invention uses a micromixer to first emulsify the edible oil and lipase to form an emulsified oil containing lipase, and improves the mass transfer efficiency between the two phases of the reactants through two micromixing operations, promotes the transesterification reaction between medium-chain triglycerides or short-chain triglycerides and the raw material oil, and improves the yield of the target product.

[0021] The present invention uses an inexpensive liquid lipase as a catalyst, and first performs microemulsification and then transesterification reaction using two micromixers. The raw materials only need 10 - 30 minutes from the start of the reaction to the completion of the reaction, realizing the continuous production of the target product. It not only improves the production efficiency, shortens the reaction time, but also ensures the product quality, and thus lays a foundation for the industrial production of liquid lipase as a catalyst to prepare medium-chain fatty acid or short-chain fatty acid structured lipids, and has important research significance and value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of the microchannel reaction system in the present invention.

[0023] In the figure: P1 is the feed pump for raw material oil; P2 is the feed pump for liquid lipase; P3 is the feed pump for medium-chain triglyceride or short-chain triglyceride; M1 is the enzyme-oil micro mixer; M2 is the reaction micro mixer; L1 is the first preheating tube; L2 is the second preheating tube; L3 is the delay tube; L4 is the quenching tube; BPV is the back pressure valve. Detailed implementation mode

[0024] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present invention, all the raw materials used are existing conventional commercially available products, and all the equipment used are commercialized laboratory and industrial equipment.

[0025] It should be noted that the structured lipid containing medium-chain fatty acids in the present invention refers to a triglyceride molecule containing at least one long-chain fatty acid and one medium-chain fatty acid, which may be a triglyceride containing one long-chain fatty acid and two medium-chain fatty acids, or a triglyceride containing two long-chain fatty acids and one medium-chain fatty acid, and the mass fraction of the medium-chain fatty acid is 18%-47%; the structured lipid containing short-chain fatty acids refers to a triglyceride molecule containing at least one long-chain fatty acid and one short-chain fatty acid, including a triglyceride containing two long-chain fatty acids and one short-chain fatty acid and a triglyceride containing one long-chain fatty acid and two short-chain fatty acids, and the mass fraction of the short-chain fatty acid is 5%-30%.

[0026] Example 1 Production method of the structured lipid containing medium-chain fatty acids according to the present invention

[0027] The production method of this example is a continuous production based on a microchannel reaction system. The microchannel reaction system includes a two-in-one-out enzyme-oil micro mixer M1 and a reaction micro mixer M2. The two feed ports of the enzyme-oil micro mixer M1 are respectively connected to the raw material oil feed pump P1 and the liquid lipase feed pump P2 through pipelines, so that the liquid lipase and the raw material oil continuously enter the enzyme-oil micro mixer M1, and the edible oil and the lipase are emulsified to form an emulsified oil containing lipase, improving the mass transfer efficiency of the lipase.

[0028] The outlet of the enzyme-oil micro mixer M1 is connected to the first inlet of the reaction micro mixer M2 through the first preheating pipe L1. The first preheating pipe L1 is used for heat exchange of the emulsified oil, and the emulsified oil after heat exchange enters the reaction micro mixer M2. The second inlet of the reaction micro mixer M2 is connected to the medium-chain triglyceride or short-chain triglyceride feed pump P3 through a feed pipeline, and a second preheating pipe L2 is arranged on the feed pipeline to preheat the medium-chain or short-chain fatty acid glyceride. The preheated medium-chain or short-chain fatty acid glyceride and the emulsified oil carry out a transesterification reaction in the reaction micro mixer M2. The outlet of the reaction micro mixer M2 is successively connected with a delay pipe L3, a quenching pipe L4 and a back pressure valve BPV through a drain pipeline. The delay function of the delay pipe L3 enables the reaction system to reach reaction equilibrium. The quenching pipe L4 has the function of inactivating the enzyme, making the liquid lipase in the reaction product lose its activity.

[0029] During actual installation, the back pressure valve BPV is a one-way valve with a pressure gauge, enabling the inactivated reaction product to be released and flow out through the back pressure valve BPV. The one-way valve is selected as the back pressure valve to effectively prevent the reaction product from flowing back.

[0030] During actual installation, the first preheating pipe L1, the second preheating pipe L2, the delay pipe L3 and the quenching pipe L4 are all made of φ3mm×6m stainless steel. During production, the preheating pipes and the delay pipe are placed in the same or a separate constant temperature water bath to ensure the reaction temperature of the reaction system. The quenching pipe is placed in another constant temperature water bath with the temperature set at 90°C to inactivate the lipase in the reaction product. Of course, during actual production, the first preheating pipe L1, the second preheating pipe L2, the delay pipe L3 and the quenching pipe L4 can also directly adopt a coil heat exchanger.

[0031] During actual installation, the raw material oil feed pump P1, the liquid lipase feed pump P2 and the medium-chain triglyceride or short-chain triglyceride feed pump P3 are high-pressure piston pumps with a working pressure greater than 5 MPa, a maximum pressure of 10 MPa, and a flow rate range of 0-200 mL / min to ensure the pressure of the whole system. The enzyme-oil micro mixer M1 and the reaction micro mixer M2 both adopt a CPMM-R600-SS type microchannel reactor with a flux of 2-40 L / h, a mixing channel size of 600 μm, a residence time of 2.256-45 ms, and an internal volume of 25 uL. The back pressure valve adopts a domestic BP30-6A11Q5W114, and the working pressure is preferably 2 MPa.

[0032] Taking soybean oil (the content of FFA in soybean oil is 1%, the content of triglyceride is 98% and the other is 1%) and medium-chain triglyceride (tricaprylin is selected in this example) as raw materials, and a liquid lipase (the lipase is a commercial lipase fermented from Aspergillus niger or Aspergillus oryzae, its enzyme activity is 100000 U / mL, and it is diluted to 10000 U / mL with distilled water before use) as a catalyst, the specific steps of the structured lipid containing medium-chain fatty acids of the present invention are described as follows:

[0033] First, pressure test the microchannel reaction system to ensure no leakage, connect the oil feed pump P1 with the raw oil storage tank, connect the lipase feed pump P2 with the diluted lipase storage tank, and connect the medium-chain triglyceride or short-chain triglyceride feed pump P3 with the medium-chain triglyceride storage tank; set the temperature of the constant temperature water bath of the first preheating tube L1, the second preheating tube L2 and the delay tube L3 at 50 °C, and set the temperature of the constant temperature water bath corresponding to the quenching tube L4 at 90 °C;

[0034] Second, use the raw oil feed pump P1 to pump soybean oil into the enzyme-oil micro mixer M1 at a flow rate of 100 g / min, and use the lipase feed pump P2 to continuously pump the diluted lipase (10000 U / mL) into the enzyme-oil micro mixer M1 at a flow rate of 6.0 g / min. At this time, soybean oil and liquid lipase are efficiently mixed in the enzyme-oil micro mixer M1 to form a microemulsion, and fatty acids (FFA), diglycerides and monoglycerides are partially generated under the catalysis of lipase; among them, fatty acids, diglycerides and monoglycerides are all amphiphilic molecules, which further promote the fusion of oil and water;

[0035] Third, when the working condition is stable, use the medium-chain triglyceride or short-chain triglyceride feed pump P3 to continuously pump tricaprylin into the reaction micro mixer M2 at a flow rate of 80 g / min, so that tricaprylin and emulsified oil undergo a transesterification reaction under the catalysis of lipase. The product coming out of the reaction micro mixer M2 reaches equilibrium through the delay tube, and then enters the molecular distillation system (the molecular distillation conditions are: the system vacuum degree is 1-10 Pa; the distillation temperature is 160-180 °C) after being quenched at a high temperature by the quenching tube L4 and passing through the back pressure valve (the pressure is set at 2 MPa), removing free fatty acids and unreacted tricaprylin, and obtaining a structured lipid containing caprylic acid, and the mass fraction of caprylic acid is 22.5%, and the content of free fatty acids is 0.3%.

[0036] Example 2 The production method of the structured lipid containing medium-chain fatty acids of the present invention

[0037] The difference between this example and Example 1 lies only in the different feeding speed ratios of soybean oil, liquid lipase, and medium-chain triglycerides (caprylic capric triglyceride in this example), and the different enzyme activities of lipase: in this example, the feeding speed of soybean oil is 150 g / min; the feeding speed of lipase (20000 U / mL) is 12 g / min; the feeding speed of caprylic capric triglyceride (MCT) is 150 g / min; the back pressure valve pressure is 2 MPa.

[0038] The reaction product was removed of free fatty acids and unreacted MCT by molecular distillation (system vacuum degree 1 - 10 Pa, distillation temperature 160 °C) to obtain a structured lipid oil containing caprylic acid and capric acid, and the mass fraction of caprylic acid was 15.5%; the mass fraction of capric acid was 20.6%; the free fatty acid content was 0.4%.

[0039] Example 3 Production method of the structured lipid containing butyric acid according to the present invention

[0040] The difference between this example and Example 1 is that: the raw material of this example is short-chain fatty acid triester (specifically tributyrin); the enzyme activity of lipase is 50000 U / mL; the feeding speed of soybean oil is 100 g / min; the feeding speed of lipase is 4.0 g / min, and the feeding speed of tributyrin is 100 g / min.

[0041] The reaction product was removed of free fatty acids and unreacted tributyrin by molecular distillation (system vacuum degree 1 - 10 Pa, distillation temperature 160 °C) to obtain a structured lipid containing butyric acid. The mass fraction of butyric acid in the structured lipid oil after molecular distillation refinement was 26.3%, and the free fatty acid content was 0.3%.

[0042] Example 4 Production method of the structured lipid containing acetic acid according to the present invention

[0043] The difference between this example and Example 1 is that: the raw material of this example is short-chain fatty acid triester (specifically triacetin); the enzyme activity of lipase is 20000 U / mL; the feeding speed of soybean oil is 100 g / min; the feeding speed of lipase is 5.0 g / min, and the feeding speed of triacetin is 50 g / min.

[0044] The reaction product was removed of free fatty acids and unreacted triacetin by molecular distillation (system vacuum degree 1 - 10 Pa, distillation temperature 160 °C) to obtain a structured lipid containing acetic acid. Among them, the acetic acid content in the structured lipid oil after molecular distillation refinement was 10.0%, and the free fatty acid content was 0.5%.

[0045] As can be seen from the above Examples 1-4, the present invention overcomes the mass transfer resistance between liquid lipase, medium-chain triglycerides (or short-chain triglycerides) and edible oil by reasonably proportioning soybean oil, lipase and medium-chain triglycerides (or short-chain triglycerides), controlling the flow rate and reasonably selecting a microchannel reactor, improving the reaction efficiency, laying a foundation for the industrialization of producing structured lipids using liquid lipase as a catalyst and medium- and short-chain fatty acid glycerides and edible oil as raw materials, and having important popularization value and economic value.

Claims

1. A method for producing a structured lipid containing medium-chain or short-chain fatty acids, characterized in that: Preparing structured oil esters containing medium-chain or short-chain fatty acids using a microchannel reaction system, comprising the following steps: S1. Set the pressures and flow rates of the raw oil feed pump (P1) and the liquid lipase feed pump (P2), then turn on the raw oil feed pump (P1) and the liquid lipase feed pump (P2) to mix the raw oil and the liquid lipase in the enzyme-oil micro mixer (M1) to form an emulsified oil containing the liquid lipase; S2. After the working conditions are stable, set the pressure and flow rate of the medium-chain triglyceride or short-chain triglyceride feed pump (P3) and turn on the medium-chain triglyceride or short-chain triglyceride feed pump (P3). The medium-chain triglyceride or short-chain triglyceride is preheated by the second preheating tube (L2) and then enters the reaction micro mixer (M2) to carry out hydrolysis and transesterification reactions with the emulsified oil. The delay tube (L3) is used to extend the reaction time to make the reaction reach equilibrium. The reaction product after the reaction is subjected to high-temperature enzyme inactivation through the quenching tube (L4), and then flows out after being released by the back pressure valve BPV to obtain the structured oil and fat containing medium-chain or short-chain fatty acids; S3. Refining of the structured oil and fat containing medium-chain or short-chain fatty acids: Distill the reaction product after high-temperature enzyme inactivation using a molecular distillation system. The distillation conditions of the molecular distillation system are: the molecular distillation vacuum degree is 1-10 Pa; the evaporation temperature of the molecular distillation is 160-180 °C; Among them, the enzyme-oil micro mixer (M1) and the reaction micro mixer (M2) are separation-recombination type or star-layer type microchannel mixers, the channel diameter ≤ 1000 μm, the liquid holding capacity is 50-1000 μL, and the flux is 4-3000 L / h; The outlet of the enzyme-oil micro mixer (M1) is connected to the first feed port of the reaction micro mixer (M2) through the first preheating tube (L1). The second feed port of the reaction micro mixer (M2) is connected to the medium-chain triglyceride or short-chain triglyceride feed pump (P3) through a feed pipeline, and a second preheating tube (L2) is arranged on the feed pipeline. The heating temperatures of the first preheating tube (L1), the second preheating tube (L2) and the delay tube (L3) are 30-70 °C; the enzyme inactivation temperature of the quenching tube (L4) is 90-100 °C; the feed flow rate ratio of the raw oil, the medium-chain triglyceride / short-chain triglyceride and the liquid lipase is 100:10-100:3-10; the addition amount of the lipase is 300-3000 U / g of oil and fat.

2. The method for producing a structured lipid containing medium-chain or short-chain fatty acids according to claim 1, characterized in that: The first preheating tube (L1), the second preheating tube (L2), the delay tube (L3) and the quenching tube (L4) are all coil heat exchangers or stainless steel coils placed in a constant temperature water bath.

3. The method for producing a structured lipid containing medium-chain or short-chain fatty acids according to claim 1, characterized in that: The raw oil is edible oil; the liquid lipase is a commercial lipase fermented by Aspergillus niger or Aspergillus oryzae through microbial fermentation; the medium-chain triglyceride includes any one or a combination of two or more of glyceryl trioctanoate, glyceryl tridecanoate or caprylic / capric triglyceride; the short-chain triglyceride includes any one or a combination of two or more of glyceryl triacetate, glyceryl tripropionate or glyceryl tributyrate.

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